U.S. patent number 6,462,770 [Application Number 09/064,667] was granted by the patent office on 2002-10-08 for imaging system with automatic gain control for reflectance and fluorescence endoscopy.
This patent grant is currently assigned to Xillix Technologies Corp.. Invention is credited to Richard W. Cline, Remy Dawson, John J. P. Fengler, Curtis B. Figley, Bruno W. Jaggi.
United States Patent |
6,462,770 |
Cline , et al. |
October 8, 2002 |
**Please see images for:
( Certificate of Correction ) ** |
Imaging system with automatic gain control for reflectance and
fluorescence endoscopy
Abstract
An imaging system for white light and fluorescence endoscopy
that includes an automatic gain control circuit 30 that adjusts the
brightness of an image produced based on distribution of pixel
intensities in one or more video frames. The magnitude of the image
signals produced by a pair of high sensitivity imaging devices such
as intensified CCD transducers are compared to a number of
reference thresholds. A time-over-threshold counter (112)
determines the number of pixels in the image signals having
magnitudes greater than or less than the reference thresholds. The
distribution of pixel intensities is supplied to a decision tree
algorithm (116) that determines whether the gain of the-intensified
CCD transducers (44a, 44b) used to produced the autofluorescence
images or the intensity of the excitation light produced by a light
source (36) should be increased or decreased. In addition, a mode
switch mechanism is provided to change rapidly from the
fluorescence imaging mode to the white light imaging mode or vice
versa. This mechanism includes provisions to prevent the accidental
application of reflected white illumination light to the
image-intensified CCD transducers. Proximity switches (192, 194)
monitor the position of a light directing mechanism such as a
mirror (186) to allow light to pass to fluorescence camera head
(42) or to a color video camera head (46). The light source is not
switched to produce white light until it is known that the mirror
is in position to direct the reflected light to the color video
camera head. Finally, the present invention produces a quantitative
display of the relative intensities of the autofluorescence light
produced in a pair of spectral bands.
Inventors: |
Cline; Richard W. (Vancouver,
CA), Fengler; John J. P. (North Vancouver,
CA), Figley; Curtis B. (Edmonton, CA),
Dawson; Remy (Vancouver, CA), Jaggi; Bruno W.
(Vancouver, CA) |
Assignee: |
Xillix Technologies Corp.
(Richmond, CA)
|
Family
ID: |
22057495 |
Appl.
No.: |
09/064,667 |
Filed: |
April 20, 1998 |
Current U.S.
Class: |
348/65 |
Current CPC
Class: |
A61B
1/00009 (20130101); A61B 1/043 (20130101); A61B
1/045 (20130101); A61B 5/0071 (20130101); A61B
5/0084 (20130101) |
Current International
Class: |
A61B
5/00 (20060101); A61B 1/045 (20060101); A62B
001/04 (); A04N 009/47 () |
Field of
Search: |
;348/29,65,66,70,76,68,74,71 ;600/101,109,117,118,160,166
;128/897,6 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 774 865 |
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May 1997 |
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EP |
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2 671 405 |
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Jul 1992 |
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FR |
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WO 95/26673 |
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Oct 1995 |
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WO |
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Primary Examiner: Kelley; Chris
Assistant Examiner: Vo; Tung
Attorney, Agent or Firm: Christensen O'Connor Johnson
Kindness PLLC
Claims
The embodiments of the invention in which an exclusive property or
privilege is claimed are defined as follows:
1. An imaging system for fluorescence endoscopy, comprising: a
light source that produces fluorescence excitation light; an
endoscope that delivers the fluorescence excitation light to tissue
under examination in vivo and collects autofluorescence produced by
the tissue; a dual channel fluorescence camera containing a first
and second high sensitivity imaging device that receive the
autofluorescence in a first and second spectral band and produce
electronic signals that are representative of the tissue under
examination; a control center, including an image processing board
that receives the electronic signals produced by the dual channel
fluorescence camera wherein said control center causes an image of
the tissue under examination to be processed, stored and displayed
on a video monitor; an automatic gain control circuit that
determines a distribution of intensity levels in the electronic
signals produced by the dual channel fluorescence camera and
adjusts a gain of the first and second high sensitivity image
device and/or adjusts a light source intensity based on said
distribution of the intensity levels such that the relative gain
between the first and second high sensitivity imaging devices
follows substantially a polynomial; and a video monitor that
receives the video signals produced by the image processing board
and displays an image of the tissue under examination.
2. The imaging system for fluorescence endoscopy of claim 1,
wherein the automatic gain control circuit comprises: a plurality
of time-over-threshold counters that determine an image area in one
or more video fields that have intensities above a plurality of
predetermined thresholds.
3. The imaging system for fluorescence endoscopy of claim 2,
wherein the time-over-threshold counters further comprise: a clock
signal having a frequency substantially equal to a pixel clock of
the dual channel fluorescence camera; a gating circuit that passes
the clock signal during an active portion of the electronic signals
produced by the dual channel fluorescence camera; a plurality of
counters that count pulses of the gated clock signal; a plurality
of comparators having the electronic signals produced by the dual
channel fluorescence camera connected to a first input and a
programmable reference voltage connected to another input such that
when the magnitude of the electronic signals exceed the reference
voltage of the comparator, the comparator produces an output which
enables one of the plurality of counters; and a processor that is
programmed to adjust a gain of the high sensitivity imaging device
and/or to adjust the light source intensity such that the
distribution of intensity levels in one or more video fields
substantially equals a desired distribution.
4. The imaging system for fluorescence endoscopy of claim 1,
wherein the light source is programmable to produce fluorescence
excitation light or white light, the system further comprising: a
color video camera coupled to receive light collected by the
endoscope; a light path directing mechanism selectively positioned
to direct light collected by the endoscope to the dual channel
fluorescence camera or to the color video camera; at least one
switch that produces a signal that is indicative of the position of
the light path directing mechanism; and a light source controller
that receives the signal from the switch and causes the light
source to produce white light after the signal produced by the
switch indicates that the light path directing mechanism is
positioned to direct the light collected by the endoscope to the
color video camera.
5. The imaging system for fluorescence endoscopy of claim 4,
wherein the light source controller causes the light source to stop
producing white light and begin producing fluorescence excitation
light before the light path directing mechanism is moved from a
position where light collected from the endoscope is directed to
the color video camera to a position where light collected from the
endoscope is directed to the dual channel fluorescence camera.
6. The imaging system for fluorescence endoscopy of claim 1,
wherein the first high sensitivity imaging device receives
autofluorescence in a first spectral band and the second high
sensitivity imaging device receives autofluorescence in a second
spectral band, the imaging system further comprising a central
processing unit that produces a quantitative indication of the
intensity of the autofluorescence light in the first spectral band
versus the intensity of autofluorescence light in the second
spectral band.
7. An imaging system for white light and fluorescence endoscopy,
comprising: a light source that produces white light and
fluorescence excitation light; an endoscope that delivers the light
to tissue under examination in vivo and collects reflected light or
autofluorescence light produced by the tissue sample; a
fluorescence camera containing a first and second high sensitivity
imaging device that receive the autofluorescence in a first and
second spectral band and produce electronic signals that are
representative of the tissue under examination; a color video
camera that receives the reflected illumination light collected by
the endoscope and produces electronic signals that are
representative of the tissue under examination; a control center,
including an image processing board, that receives the electronic
signals produced by the dual channel fluorescence camera or the
color video camera and said control center causes an image of the
tissue under examination to be processed, stored and displayed on a
video monitor; a mode switch mechanism including: (i) a light
director that is selectively positioned to direct light collected
by the endoscope to the fluorescence camera or to the color video
camera; (ii) a sensing mechanism that senses the position of the
light director; and (iii) a mechanism that operates to change the
light source to produce either fluorescence excitation light or
white light according to the sensed position of the light director
in order to protect the fluorescence camera from reflected white
light; and a video monitor that receives video signals produced by
the image processing board and displays an image of the tissue
under examination.
8. The imaging system for white light and fluorescence endoscopy of
claim 7, further comprising: an automatic gain control circuit
within the control center that determines a distribution of
intensity levels in the electronic signals produced by the first
and second high sensitivity imaging devices and adjusts a gain of
the high sensitivity imaging devices and/or adjusts the light
source intensity based on said distribution of intensity levels
such that the relative gain between the first and second high
sensitivity imaging devices follows substantially a polynomial.
9. The imaging system for white light and fluorescence endoscopy of
claim 8, wherein the automatic gain control circuit comprises: a
plurality of time-over-threshold counters that determine an image
area in one or more video fields that have intensities above a
plurality of predetermined thresholds.
10. The imaging system for white light and fluorescence endoscopy
of claim 9, wherein the time-over-threshold counters further
comprise: a clock signal having a frequency substantially equal to
a pixel clock of the first and second high sensitivity imaging
devices; a gating circuit that passes the clock signal during an
active portion of the electronic signals produced by the dual
channel fluorescence camera; a plurality of counters that count
pulses of the gated clock signal; a plurality of comparators having
the electronic signals produced by the dual channel fluorescence
camera connected to a first input and a programmable reference
voltage connected to another input such that when the magnitude of
the electronic signals exceed the reference voltage of the
comparator, the comparator produces an output which enables one of
the plurality of counters; and a processor that is programmed to
adjust a gain of the high sensitivity imaging devices and/or to
adjust the light source intensity such that the distribution of
intensity levels in one or more video fields substantially equals a
desired distribution.
11. An imaging system for fluorescence endoscopy, comprising: a
light source that produces fluorescence excitation light; an
endoscope that delivers the fluorescence excitation light to tissue
under examination in vivo and collects autofluorescence produced by
the tissue; a dual channel fluorescence camera containing a first
and second high sensitivity imaging device that receive the
autofluorescence in a first and second spectral band and produce
electronic signals that are representative of the tissue under
examination; a control center including an image processing board
that receives the electronic signals produced by the dual channel
fluorescence camera wherein said control center causes an image of
the tissue under examination to be displayed on a video monitor; an
automated gain control circuit that determines the distribution of
intensity levels in the electronic signals produced by the dual
channel fluorescence camera and adjusts the gain of the first and
second high sensitivity imaging device and/or adjusts a light
source intensity based on the distribution of intensity levels such
that the relative gain between the first and second high
sensitivity imaging device follows substantially a polynomial, the
automatic gain control circuit including: (a) a plurality of
time-over-threshold counters that determine an area in one or more
video fields having intensities above a plurality of predetermined
thresholds, the time-over-threshold counters including a clock
signal having a frequency substantially equal to a pixel clock of a
dual channel fluorescence camera; (b) a gating circuit that passes
the clock signal during an active portion of the electronic signals
produced by the dual channel fluorescence camera; (c) a plurality
of counters that count pulses of the gated clock signals; (d) a
plurality of comparators having the electronic signals produced by
the dual channel fluorescence camera connected to a first input and
a programmable reference voltage connected to another input such
that when the magnitude of the electronic signals exceed the
reference voltage of the comparator, the comparator produces an
output that enables one of the plurality of counters; and (e) a
processor that is programmed to adjust the gain of the high
sensitivity imaging devices and/or to adjust the light source
intensity such that the distribution of intensity levels in one or
more video fields substantially equals a desired distribution.
12. An imaging system for white light and fluorescence endoscopy,
comprising: a light source that produces white light and
fluorescence excitation light; an endoscope that delivers the light
to the tissue under examination in vivo and collects reflected
light or autofluorescence light produced by the tissue sample; a
fluorescence camera containing a first and second high sensitivity
imaging device that receive the autofluorescence in a first and
second spectral band and produce electronic signals that are
representative of the tissue under examination; a color video
camera that receives the reflected illumination light collected by
the endoscope and produces electronic signals that are
representative of the tissue under examination; a control center,
including an imaging processing board, that receives the electronic
signals produced by the dual channel fluorescence camera or the
color video camera, and said control center causes an image of the
tissue under examination to be processed, stored and displayed on a
video monitor; an automatic gain control circuit within the control
center that determines a distribution of intensity levels in the
electronic signals produced by the first and second high
sensitivity imaging devices and adjusts a gain of the high
sensitivity imaging devices and/or adjusts the light source
intensity based on the distribution of intensity levels such that
the relative gain between the first and second high sensitivity
imaging devices follows substantially a polynomial, the automated
gain control circuit including: a plurality of time-over-threshold
counters that determine an image area in one or more video fields
having intensities above a plurality of predetermined thresholds,
the time-over-threshold counters including; a clock signal having a
frequency substantially equal to a pixel clock of the first and
second high sensitivity imaging devices; a gating circuit that
passes the clock signal during an active portion of the electronic
signals produced by the dual channel fluorescence camera; a
plurality of counters that count pulses of the gated clock signal;
a plurality of comparators having the electronic signals produced
by the dual channel fluorescence camera connected to a first input
and a programmable reference voltage connected to another input
such that when the magnitude of the electronic signals exceeds the
reference voltage of the comparator, the comparator produces an
output which enables one of the plurality of counters; and a
processor that is programmed to adjust the gain of the high
sensitivity imaging devices and/or to adjust the light source and
intensity such that the distribution and intensity levels in one or
more video fields substantially equals a desired distribution; a
mode switch mechanism including: (i) a light detector that is
selectively positioned to direct light collected by the endoscope
to the fluorescence camera or to the color video camera; and (ii) a
mechanism that operates to change the light source to produce
either fluorescence excitation light or white light according to
the position of the light director; and a video monitor that
receives the signals produced by the image processing board and
displays an image of the tissue under examination.
13. An autofluorescence imaging system, comprising: a light source
that produces excitation light; an endoscope that delivers the
excitation light to tissue under examination in vivo and collects
autofluorescence produced by the tissue; a dual channel
fluorescence camera having a first and second imaging device having
pixels that produce signals in response to applied light and a beam
splitter for dividing the autofluorescence into a first and second
spectral band such that the first imaging device receives the
autofluorescence in the first spectral band and the second imaging
device receives the autofluorescence in the second spectral band;
an automatic gain control circuit that adjusts the gain of the
first and second imaging devices based on a distribution of pixel
intensity levels within an image area of the signals produced by
the first and second imaging devices in response to the first and
second spectral bands of autofluorescence such that the gain of the
first and second imaging devices follows substantially a
polynomial; an image processing board that receives electronic
signals produced by the first and second imaging devices and
produces corresponding video signals; and a video monitor that
receives the video signals from the imaging processing board and
displays an image of the tissue.
14. The autofluorescence imaging system of claim 13, wherein the
distribution includes a number of pixels within the image area of
each of the first and second imaging devices having intensities
that are greater than a desired peak value and a desired average
value within the image area.
15. An autofluorescence imaging system, comprising: a light source
that produces white light and excitation light; an endoscope that
directs the excitation light to a tissue sample in vivo and
collects autofluorescence produced by the tissue; a dual channel
fluorescence camera, including a first and second imaging device
having pixels that produce signals in response to applied light and
a beam splitter for splitting the autofluorescence into to a first
and second spectral band and simultaneously directing
autofluorescence in a first spectral band to the first imaging
device and autofluorescence in the second spectral band to the
second imaging device; a color video camera that receives reflected
white light collected by the endoscope and produces electronic
signals that are representative of the tissue under examination; a
mode switch having: (i) a light director that is selectively
positioned to direct light collected by the endoscope to the dual
channel fluorescence camera or to the color video camera; (ii) one
or more detectors for detecting the position of the light director;
(iii) a mechanism that operates to change the light source to
produce either fluorescence excitation light or white light,
according to the detected position of the light director; an
automatic gain control circuit for adjusting a gain of the first
and second imaging device based on an intensity distribution of
pixel values within an image area of the signals produced by the
first and second imaging devices in response to the
autofluorescence light in the first and second spectral bands; an
image processing board that receives signals from each of the first
and second imaging devices and produces corresponding video
signals; and a video monitor that receives the video signals and
displays an image of the tissue sample.
16. An autofluorescence imaging system comprising: a light source
that produces excitation light; an endoscope that directs the
excitation light to a tissue sample in vivo and collects
autofluorescence produced by the tissue; a dual channel camera
including a first and second high sensitivity image detector having
pixels that produce signals in response to applied autofluorescence
and a beam splitter for splitting the autofluorescence into a first
and second spectral band and for directing the autofluorescence in
the first spectral band to the first image detector, and the
autofluorescence in the second spectral band to the second image
detector; an image processing board that receives signals from each
of the first and second image detectors and produces corresponding
video signals; and means for determining a distribution of
pixel-intensity values in an image area of the signals produced by
the first and second image detectors and for adjusting the relative
gain of the first and second image detectors and/or the intensity
of the excitation light based on the distribution determined such
that the gain between the first and second image detectors follows
substantially a polynomial.
17. The system of claim 16, wherein the gain of the first and
second image detectors and/or intensity of the excitation light are
adjusted such that the distribution includes a number of pixels
within the image area having intensities that are greater than a
desired peak value and number of pixels with a desired average
value.
18. An autofluorescence imaging system comprising: a light source
that produces excitation light; an endoscope that directs the
excitation light to a tissue sample in vivo and collects
autofluorescence produced by the tissue; an autofluorescence
camera, including a first and second image detectors, that produces
an image of the tissue; and an automatic gain control circuit that
determines a distribution of pixel intensity values in an area of
the image produced by the autofluorescence camera and adjusts the
gain of the first and second image detectors and/or the intensity
of the excitation light based on the determined pixel intensity
distribution such that the gain of the first and second image
detectors maintains a substantially polynomial.
Description
FIELD OF THE INVENTION
The present invention relates to imaging systems for medical
endoscopy, in general and to endoscopic imaging systems for
fluorescence and reflectance endoscopy, in particular.
BACKGROUND OF THE INVENTION
One common diagnostic technique used by physicians to detect
diseases within a body cavity of a patient is white light optical
fiber endoscopy. With this technique, white light is directed into
the body cavity via a non-coherent fiber-optic illumination guide
of an endoscope. The light illuminates the tissue under examination
and the reflected illumination light is gathered and transmitted
through a coherent fiber-optic imaging guide of the endoscope. The
image formed by the reflected white light at the end of the imaging
guide may be viewed directly through the endoscope eyepiece or may
be imaged by a color video camera connected to the eyepiece. Images
transduced by the camera are then typically transmitted to an image
processing/storage device and to a video monitor where they can be
viewed by the physician.
To aid physicians performing endoscopy in detecting the presence of
cancerous or pre-cancerous tissue, the differences in the
autofluorescence (also referred to as native fluorescence) spectrum
of normal and abnormal tissue can be exploited. In fluorescence
optical fiber endoscopy, a fluorescence excitation light is
delivered into the body cavity via the illumination guide of the
endoscope. The wavelengths of this light are matched to the
absorption spectrum of the naturally occurring fluorescing
molecules (or fluorophores) present in the tissue (i.e., to blue
light). The fluorescence excitation light causes the tissue in the
body cavity to fluoresce with a green and red emission spectrum and
the resulting light is collected and transmitted through the
optical fiber imaging guide of the endoscope. The resulting image
is transduced by a camera that filters out any reflected blue light
and divides the autofluorescence into two broad (green and red)
spectral bands. The image formed by the light in each spectral band
is projected onto a separate intensified CCD (ICCD) transducer and
the resulting signal is fed into a control center for processing,
storage and, finally, for display on a video monitor. The
difference in the autofluorescence emission spectrum of normal and
abnormal tissue is presented as a difference in color on the video
monitor.
Systems for fluorescence fiber endoscopy are fully described in
U.S. Pat. Nos. 5,507,287; 5,590,660, 5,647,368 and 4,786,813 that
are assigned to Xillix Technologies Corp. of Richmond, BC, Canada,
the assignee of the present invention, and are sold by Xllix as the
Xillix.RTM. LIFE-Lung Fluorescence Endoscopy System.RTM. (the
"LIFE-Lung System"). Multi-center clinical trials have shown that
by using the Xllix LFE-Lung System as an adjunct to white light
endoscopy, the physician's sensitivity in detecting moderate
dysplasia, or worse, is 2.71 times greater than the sensitivity of
a physician using white light endoscopy alone.
The current LIFE-Lung System has a number of limitations, however.
First, the current embodiment of the system requires the physician
to manually adjust the gain of the system (i.e., to increase and
decrease the camera's sensitivity to the tissue autofluorescence).
This is a cumbersome task for the physician to perform, when he/she
is simultaneously trying to maneuver the endoscope in the patient.
Although automatic gain control circuits for video systems are
widely available, they do not provide adequate gain control for the
complex scene conditions encountered in imaging autofluorescence
with ICCDs. If, for example, the average brightness of an image is
increased to an acceptable level, there may be bright spots that
can damage the ICCDs. Similarly, if the peak brightness of an image
is reduced to prevent localized image saturation, the remainder of
the image may become too dark to be recognizable. Furthermore,
commonly available average and peak-based automatic gain control
circuits do not provide images with a good dynamic range under a
variety of viewing conditions, i.e. with an optimized contrast. In
endoscopy, these viewing conditions include situations whereby the
range of fluorescence light intensities are greater than the
dynamic range of ICCDs and the image scenes vary from complex
structures (i.e. lots of intensity variations) to flat structures
(i.e. homogeneous).
A further complication with the use of an automatic gain control
circuit arises due to the fact that the gain relationship between
the two channels (green and red) of the imaging system must follow
a defined function. If the gain of each channel is varied
independently, the colors in the resulting video image will not
consistently reflect the spectral differences in the
autofluorescence of the tissue.
A second limitation of the current LIFE-Lung System becomes evident
when a physician wishes to switch between white light (reflectance)
and fluorescence imaging modes. With the current system, the
physician must switch light sources and cameras manually (i.e.,
from a white light illumination source to a fluorescence excitation
light source and from an RGB color video camera to the fluorescence
camera). One technique for addressing this time consuming process
is to have all light sources and cameras connected to the endoscope
simultaneously and to utilize a mode switching mechanism to switch
from one imaging mode to the other. However, some precaution must
be taken in the implementation of a switching mechanism since the
ICCDs can be damaged if they are subjected to the bright, reflected
illumination light. Care must be taken to ensure that the ICCDs are
not energized unless the appropriate illumination conditions
exist.
A third limitation of the current LIFE-Lung System is that a
physician viewing the image displayed by the system has no way of
objectively quantifying the extent of abnormality exhibited by the
tissue under examination. The effective use of the system is
dependent on such subjective factors as the physician's ability to
distinguish color and his/her ability to interpret this color
information in the context of other image features. A means to
objectively quantify the difference in the autofluorescence spectra
of normal and abnormal tissue, or even an additional means to
subjectively differentiate these tissues based on their difference
in autofluorescence spectra could improve the clinical usability of
this system. This can be accomplished using computational
techniques using the spectral information of the emitted
fluorescence and displaying the results on the monitor together
with the images.
In summary, the operation of current fluorescence endoscopy systems
may be significantly improved by: a) an automatic gain control
circuit that will optimally adjust the brightness of
autofluorescence images and that will maintain a defined
relationship between the two channels of the imaging system; b) a
mechanism that allows rapid switching between white light and
fluorescence imaging modes, while preventing the accidental
exposure of energized ICCDs to damaging light intensities; and c) a
means of utilizing the differences in the autofluorescence emission
spectra of normal to abnormal tissue to objectively quantify the
degree of abnormality of the tissue.
SUMMARY OF THE INVENTION
The present invention is an imaging system for white light and
fluorescence endoscopy that includes a particular automatic gain
control (AGC) circuit in the fluorescence imaging mode. The AGC
circuit adjusts the gain of the imaging system by adjusting the
gain of two high sensitivity imaging devices such as image
intensified CCD (ICCDs) transducers in a fluorescence camera head
and by adjusting the light intensity of the excitation light
source. The video signals from a pair channels (the "green" and
"red" channel) of a fluorescence camera are supplied to a set of
counters. The counters, consisting of counters connected to a
clocking oscillator, measure the length of time each video signal
has a magnitude that exceeds a reference threshold that is
individually set for each counter. Thus, by appropriately arranging
the threshold levels, the outputs of the counters can be made to
indicate the distribution of video signal amplitudes in one or more
video fields. Based upon the outputs of the counters, a decision
tree algorithm determines if the gain of the imaging system or the
light source intensity should be increased or decreased. A gain
control equation determines the appropriate value of light source
intensity change and maps the resulting imaging system gain
increase or decrease to an individual gain change for each ICCD
transducer such that the relative gain between the two channels
remains the same.
The present invention also includes a mode switching mechanism that
allows for convenient switching between white light and
fluorescence endoscopy imaging modes. The implementation of mode
switching implies that white light and fluorescence light sources
and cameras are connected to the endoscope simultaneously and that
the appropriate combination of camera and light source are
activated when switching modes. This requires a two-part mode
switching mechanism: one switching the cameras and one switching
the light sources. The camera mode switching mechanism consists of
a light directing mechanism such as a mirror that is movable
between a first position, where the image from the endoscope is
reflected towards an RGB video camera head, and a second position,
where the image from the endoscope is allowed to pass to the
fluorescence camera head. When a physician uses the mode switch to
change from white light imaging to fluorescence imaging or vice
versa, a pair of proximity switches provide signals to the system
control center, which monitors the position of the mirror, to
ensure that the ICCDs are not energized until the appropriate light
source has been selected. The light source mode switching mechanism
consists of a filter driver that positions blue, fluorescence
excitation filters or white light filters in an illumination light
path that extends between the light source and an endoscope.
The present invention also provides a means of objectively
quantifying the spectral differences between normal and abnormal
tissue by using the relative brightness of autofluorescence in the
spectral bands being imaged (green and red). A portion of the
autofluorescence image is analyzed and the numerical value defined
by a particular mathematical function such as the ratio of the
image brightnesses of the two wavebands is displayed for the
physician.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing aspects and many of the attendant advantages of this
invention will become more readily appreciated as the same becomes
better understood by reference to the following detailed
description, when taken in conjunction with the accompanying
drawings, wherein:
FIG. 1 is a block diagram of an imaging system for white light and
fluorescence endoscopy according to the present invention;
FIG. 2 is a block diagram of a light source used in the imaging
system for white light and fluorescence endoscopy shown in FIG.
1;
FIG. 3 is a block diagram of an automatic gain control circuit in
accordance with a first aspect of the present invention;
FIG. 4 is a block diagram of a number of comparators and time-over
threshold counters that are included in the automatic gain control
circuit shown in FIG. 3;
FIG. 5 is a flowchart illustrating the steps performed by the
present invention to change the gain of the imaging system shown in
FIG. 3 or the intensity of light produced by the light source shown
in FIG. 2;
FIG. 6 is a block diagram of an imaging mode switching mechanism
located in the combination camera head in accordance with another
aspect of the present invention; and
FIG. 7 is a pictorial illustration of an autofluorescence image
that includes a quantitative indication of the relative intensities
of the autofluorescence light present in two spectral bands in
accordance with another aspect of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention is an imaging system for white light and
fluorescence endoscopy that includes an automatic gain control
(AGC) circuit in the fluorescence imaging mode. The AGC circuit
controls the image brightness in two ways, a) by adjusting the gain
of the two image-intensified CCDs (ICCDs) transducers in a
fluorescence camera head, and b) by adjusting the intensity of an
excitation light source. The input to the AGC circuit are the two
video signals (a green and red channel) produced by the
fluorescence camera. The video signals are supplied to a set of
counters that determine a total period of time during which the
video signal has a magnitude that exceeds reference threshold (set
individually for each counter). The outputs of the counters are
indicative of the distribution of video signal amplitudes in one or
more video fields. Based upon the outputs of the counters, a
decision tree algorithm determines if the gain of the imaging
system or light source intensity should be increased or decreased.
A gain control equation determines the appropriate value of light
source intensity change and maps the gain increase or decrease to
an individual gain change for each ICCD such that the relative gain
between the two channels remains the same.
FIG. 1 is a block diagram of an imaging system 10 for white light
and fluorescence endoscopy according to the present invention. At
the heart of the imaging system is a control center 20 that
includes a central processing unit 22 that is programmed to control
the operation of the system including a combination light source 36
and a combination camera head 42. An internal random access memory
(RAM), a hard disk drive and read-only memory (ROM) 24 stores a
computer software program that controls the operation of the
central processing unit 22. The memory also allows the storage of
data such as acquired images, parameters and log files. A number of
controls 26 on a front panel of the control center 20, allow an
operator to adjust the operation of the imaging system.
The control center 20 also includes an imaging board 28 that
receives analog video signals that originate from a number of
sources including a fluorescence camera head 44 and an RGB camera
head 46 that are enclosed within the combination camera head 42. A
video switch, that is part of a digital and video I/O 32, receives
and selects the fluorescence or RGB video signals to be supplied as
an input to the imaging board. The imaging board 28 digitizes the
selected video signal, then processes and converts the digitized
signals to appropriate signals to be displayed on a video monitor
54.
An automatic gain control circuit 30, included within the control
center 20, automatically adjusts the gain of the autofluorescence
camera head 44 and the intensity of the fluorescence excitation
light from the combination light source 36.
The combination light source 36 provides the white light and
fluorescence excitation light. The control center 20 is interfaced
with the light source 36 through status and control lines 102, 106,
and 108. Broadband white illumination light or fluorescence
excitation light (typically at 437 nm.+-.10 nm) is supplied from
the combination light source 36 to an illumination guide 38 of a
fiber-optic endoscope 40. Light from the illumination guide 38
illuminates an internal body cavity of a patient. Reflected white
light or autofluorescence light from the tissue under examination
is transmitted by an imaging guide of the fiber-optic endoscope 40
and is projected onto the combination camera head 42. The
combination camera head 42 also includes a mode switch mechanism 67
that directs the light received from the endoscope 40 to either the
RGB video camera head 46 or the fluorescence camera head 44. With
the fluorescence imaging mode selected, the fluorescence camera
head 44 produces electronic signals that are routed to a dual
channel fluorescence camera control unit within the control center
20 (not shown) that converts the electronic signals to standard
video signals. The video signals are then routed through the video
I/O 32 to the imaging board 28 where they are processed before
being displayed on the RGB video monitor 54. Alternatively, if the
physician desires to view a reflectance white light image, the
position of the mode switch mechanism 67 is selected to project the
reflected illumination light onto an RGB video camera head 46. The
electronic signals produced by the camera head 46 are supplied to
an RGB camera control unit 48 that is external to the control
center 20, where they are converted to RGB video signals. The white
light RGB video signals are also routed through the video I/O 32 to
the imaging board 28 and are processed before being displayed on
the RGB video monitor 54. The RGB video camera control unit 48
includes an automatic gain control circuit that also has the
capability of adjusting the intensity of the light produced by the
combination light source 36 when the system is operating in white
light mode. The automatic gain control signals for the white light
mode are transmitted to the combination light source on a lead
110.
A keyboard 52 interfaces with the control center 20 through the
digital I/O 32 on the computer motherboard and allows the operator
to enter patient data or to change the operating parameters of the
imaging system.
In order to display the white light and fluorescence images, the
RGB video monitor 54 is connected to the control center 20 through
the video I/O 32. A VCR 56 may be connected so that video images
can be recorded for later review and analysis. A video printer 58
allows a physician to print hard copies of a video frame. Images
may also be recorded by a film recorder 60 or stored on a
magneto-optical disk 62.
To allow a user to control the operation of the imaging system,
several programmable operator input devices are provided. A
footswitch 64 and three operator control switches 65 on the camera
head 42 allow the operator to remotely activate various control
center 20 functions such as freezing and storing images, selecting
different AGC modes, or to control some of the peripheral devices
such as the video printer 58, film recorder 60, or magneto optical
disk 62.
FIG. 2 illustrates in further detail the combination light source
36 that is shown in FIG. 1. The light source includes a metal
halide lamp 80 that produces broadband white light with mercury
(Hg) peaks. Light produced by the lamp 80 is passed through a
number of filters 82. Depending on the imaging mode selected, the
light is transmitted through either a broadband white light filter
(i.e. triple notch filter to remove the Hg peaks) that eliminates
the Hg peaks and shapes the spectrum of the metal halide lamp so
that it is similar to that of a Xenon lamp. Alternatively, if
fluorescence imaging is selected, light from the lamp is passed
through a blue fluorescence excitation light filter that comprises
a blue pass band having a center frequency near the mercury peak
that occurs at 437 nanometers.
Light passing through the filters 82, also passes through an
adjustable intensity control mechanism 84, which controls the
intensity of the light delivered to an endoscope. The intensity
control 84 is preferably a metal plate with an appropriate shape to
block a variable amount of light when it is moved in and out of the
light path.
After passing through the intensity control mechanism 84, the light
passes through a shutter mechanism 86 that opens to allow the light
to enter the illumination guide of the endoscope, if the latter is
plugged in.
The operation of the combination light source 36 is controlled by a
microprocessor-based light source controller 90. The light source
controller 90 controls the operation of a metal halide lamp ballast
92 that provides the operating voltage for the metal halide lamp
80. In addition, the light source controller provides control
signals to a filter driver 94, that physically moves one of the
filters 82 into the light path in accordance with time imaging mode
selected.
An intensity control driver 96 receives control signals from the
light source controller 90 in order to move the intensity control
84 in and out of the light path, and thereby varies the intensity
of the light that reaches the illumination guide of the endoscope.
The light source controller 90 also sends control signals to a
shutter driver/motor 98 that causes the shutter mechanism 86 to
open and close.
In addition to controlling the components that adjust the intensity
and wavelength of light that is provided to the illumination guide
of the endoscope, the light source controller 90 also interfaces
with a number of front panel switches 100 that allow a physician to
manually adjust the operation of the light source. Alternatively,
the light source controller 90 receives commands to control the
light source from an interface to the status and control lines 102
that is coupled to the control center 20 that controls the overall
operation of the imaging system as shown in FIG. 1.
To change the output of the combination light source 36 from white
illumination light to blue excitation light or vice versa, as well
as to control the intensity of the light produced, the light source
controller 90 also receives control signals from the control center
on lead 106 that indicate which of the filters 82 should be placed
into the light path in order to create the white light illumination
or blue excitation light. The light source controller 90 receives
signals from the control center on the status and control lines 108
that indicate whether the intensity of the excitation light
produced should be increased or decreased. Finally, the light
source controller 90 receives signals from the RGB video camera
control unit 48 on the lead 110 that adjusts the intensity of the
white illumination light produced.
To eliminate the need for a physician to manually adjust the gain
while in the fluorescence imaging mode, the imaging system of the
present invention includes a fluorescence mode automatic gain
control (AGC) circuit 30 as shown in FIG. 3. The imaging system can
also be operated under manual control as the current Xillix
LIFE-Lung Fluorescence Endoscopy System.RTM.. The implementation of
the fluorescence mode AGC is as follows: As described previously,
autofluorescence light produced by the tissue under examination is
divided into a pair of spectral bands and projected onto a pair of
high sensitivity imaging devices such as a pair of electron
bombarded CCD's or image intensified CCD transducers 44a and 44b.
The transducer 44a receives the light in a wavelength band
.DELTA..lambda..sub.1, which is located in the green portion of the
visible spectrum, while the transducer 44b receives light in a
wavelength band .DELTA..lambda..sub.2, which is located in the red
portion of the visible spectrum. The electronic signals produced by
the intensified CCD transducers 44a and 44b are supplied to camera
control units (CCUs) 45a and 45b within the control center 20,
where they are converted into video signals and routed through the
video I/O 32 to the imaging board 28 and to the AGC circuit.
The video signals routed to the AGC circuit are applied to a
time-over-threshold counter circuit 112. The counter circuit also
receives a clock signal which is gated by the horizontal and
vertical sync signals from the CCUs. The counter 112 produces a
number of outputs #T1, #T2, . . . #Tn, each of which contains a
value which is proportional to the area in one or more video fields
that has an intensity level above an associated predefined
threshold intensity value. Each of the output values #T1, . . .
#Tn, may be weighted by a function a.sub.1, . . . a.sub.n 114
before being supplied to a decision tree algorithm 116. The
decision tree algorithm 116 determines if the gain of the imaging
system and/or the intensity of the light produced by the
combination light source 36 should be increased or decreased. The
output of the decision tree algorithm 116 indicates the amount by
which the gain should be increased/decreased and this signal is
supplied to a gain control equation 120. The gain control
calculates the amount by which the light source intensity and/or
the gain of the individual intensified CCD transducers 44a and 44b
of the imaging system should be adjusted to meet the gain change
determined by the decision tree algorithm, while maintaining a
predefined gain relationship between the two channels.
If the camera gain is to be increased or decreased, the gain
control equation 120 produces a pair of binary numbers whose
magnitude will result in a proportional gain change in the two
ICCDs. An increase/decrease gain control circuit 122 receives the
binary numbers from the gain control equation 120 and converts the
binary numbers received into a pair of voltage levels that are
supplied to a pair of transducer gain controls 124 and 126. The
transducer gain controls 124 and 126 adjust the absolute gain of
the intensified CCD transducers 44a and 44b respectively.
FIG. 4 illustrates in greater detail the time-over-threshold
counter 112 described above. The counter 112 operates to produce
numeric counts that are indicative of how long a threshold
intensity is exceeded in one or more video frames. These numeric
counts are proportional to the area in an image with an intensity
above a predefined value. A bank of independently programmable,
reference threshold digital-to-analog converters 140 is programmed
by the control center 20 to set a series of reference threshold
levels against which the video signals from the CCUs are compared.
The particular reference threshold levels are selected to represent
a percentage of the zero to full scale video signal that is
produced by the CCUs and their chosen values are generally
dependent on the type of tissue being examined, as will be
described below.
The reference thresholds are applied to the inverting inputs of a
number of comparators 144. For example, a voltage equal to 45% of
the full scale range of the green channel video signal is supplied
on a lead 142a to an inverting input of a comparator 144a.
Similarly, a voltage equal to 75% of the full scale range is
supplied on a lead 142b to an inverting input of a comparator 144b.
Another set of reference threshold voltages are applied to a set of
comparators that receive the video signal produced by the red
channel CCU. In the presently preferred embodiment of the
invention, one reference threshold for each channel is set at a
desired peak value while the other reference threshold is set at a
desired average intensity value.
The video signals produced by the dual channel fluorescence CCUs
are applied to the noninverting inputs of the comparator circuits
144. When the voltage level of the video signals exceeds the
reference thresholds set by the digital-to-analog converters 140,
the comparators 144 produce logic high signals. Associated with
each of the comparators 144 is a 24-bit counter 146. Each counter
has a counter enable pin coupled to the output of its associated
comparator such that when the comparator produces the logic high
signal, the counter is enabled.
As indicated above, the automatic gain control circuit 30 includes
a free running clock 150 having a frequency that is substantially
equal to the pixel clock of the CCUs. A sync delay and gating
circuit 152 receives the horizontal and vertical synchronization
signals produced by the CCUs and only passes the free running clock
150, during the active portions of the video signals. The sync
delay and gating circuit 152 also produces a field clock pulse for
each field of the video signals received. The pulses are counted by
a short counter 154 in order to keep track of the number of field
periods associated with the values contained in the
time-over-threshold counters.
When the counters 146 are enabled by their corresponding comparator
circuits 144, the counters 146 count the number of sync-gated clock
pulses that occur during the time when the video signals produced
by the red or green channel CCUs exceed the reference threshold
associated with the comparator that is connected to the counter's
enable pin.
The values in the counters 146 are read out through a counter
readout control circuit 160 that connects the counters 146 to the
imaging system's data bus 130 located on a motherboard within the
control center 20. The counter readout control circuit also
receives the count held in the short counter 154. The short counter
154 allows the software to be programmed to read out the counters
146 at periodic intervals, such as every ten fields, etc.
Although the presently preferred embodiment of the invention
utilizes two reference thresholds for each of the green and red
channels, additional threshold counters can be added to the
automatic gain control circuit in the manner described above if it
is desired to obtain more detailed information on the distribution
of the video signal amplitudes.
FIG. 5 illustrates the steps performed by the decision tree
algorithm 116 and the gain control equation 120 shown in FIG. 3 to
adjust the gain of the ICCDs and the light source intensity. FIG. 5
illustrates the two basic processes used to implement the automatic
gain control, namely, i) the setup of the parameters in steps 162
and 164, and ii) the running of the decision tree algorithm and
gain control equation in steps 166 to 172.
Beginning with a step 162, the peak and average reference
thresholds are set. These values are selected by the operator using
the system software. The values selected depend upon the type of
image being viewed. In an image that contains many structural
features, the thresholds are selected to ensure that all details
remain visible. For example, when viewing a body cavity containing
detailed structure such as the bronchi, the peak reference
threshold may be set at 90% of the full scale value and the average
reference threshold set at 50% of the full scale value.
Alternatively, if the body cavity being examined is relatively
homogeneous, such as the stomach, the reference threshold values
may be set such that the average intensity of the image ensures a
relatively bright image. For example, the peak reference threshold
may be set at 80% of full scale and the average reference threshold
set at 60% of full scale. Preprogrammed thresholds selected for
commonly viewed tissue samples can be selected or custom values can
be entered.
At a step 164, the automatic gain control circuit selects a number
of AGC image fill goal values. These values represent the nominal
image area for which the video signal amplitude must be greater
than or equal to a particular threshold. For example, fill goal
values may be chosen such that 2% of the image area has video
signal amplitudes greater than the peak threshold value and 55% of
the image area has video signal amplitudes greater than the average
threshold value. The automatic gain control circuit adjusts the
gain of the ICCDs and/or the intensity of the light source such
that the image intensity distribution calculated from the
time-over-threshold counter 112 achieves the best match to the
desired image fill goal values. Like the threshold values, the fill
goal values are selected by the operator of the system.
Step 166 is the first step in the actual AGC decision tree
algorithm. At a step 166, the automatic gain control circuit waits
for the last gain change to take effect and then measures the image
intensity distribution for specified number fields. At the end of
the specified number fields, the values from the counters 146 in
the time-over-threshold counter circuit 112 are read and the image
areas analyzed.
The image area having video signal amplitudes above the higher, or
"peak" threshold, and the image area having video signal amplitudes
above the lower, or "average" threshold, are applied to the
decision tree at step 168. The decision tree determines whether the
gain should be changed so that the intensity distribution will
better meet the AGC fill goal values desired. As discussed above,
the image area allowed to exceed the peak or the average threshold
may be weighted by the functions 114, in order to make the
automatic gain control circuit operate more like a peak or average
value control circuit as desired for the particular viewing
situation.
The amount of gain change determined by the decision tree algorithm
116 is modified by well known process control techniques at a step
170 to optimize transient behavior such as overshoot, settling
time, and oscillatory behavior. These techniques include a leaky
integrator function, deadband control, control function mapping,
proportional control, and rate and range limiting actions on the
next applied gain change. These techniques ensure gain changes
occur as quickly as possible without creating stability
problems.
At a step 172, the gain change for the green or red channel ICCD is
determined and if required, the amount of light source intensity
change. The gain change is modified by the control techniques and
is applied to the gain control equation 120. This equation relates
the gain setting of the ICCD in each of the two channels, such that
the ratio (first order polynomial) of the gains between the two
channels is maintained. The ratio of the gains between the two
channels may be selected by the system operator. The operator may
adjust the ratio, such that the resulting video image appears more
red or more green as desired. In the presently preferred embodiment
of the invention, the relative gain of the ICCD in the red channel
to the ICCD in the green channel can be varied over a range of 0.75
to 3. In some applications, the relationship between the gains of
the two channels may be a higher order polynomial, e.g. g.sub.1
=c+ag.sub.2 +bg.sub.2.sup.2 +. . . where g.sub.1 is the gain of the
red channel, g.sub.2 is the gain of the green channel and a, b, c,
are constants.
The situation may occur that the required fluorescence camera gain
falls outside of the optimal gain adjustment range of the ICCD in
one or both of the channels. If the calculated gain setting of
either channel is greater than the maximum optimal setting or
smaller than the minimum optimal setting, then the intensity of the
excitation light source is increased or decreased by a fixed
amount. The intensity of the light produced by the light source is
adjusted a sufficient amount to return the camera gain settings to
within the optimal working range. A pseudocode listing of the
decision tree algorithm 116 and gain control equation 120 is set
forth in Appendix A.
The present invention also includes a two part mode switch
mechanism (one part in the light source and one part in the
combination camera head) that allows for convenient switching
between white light and fluorescence endoscopy imaging modes. FIG.
6 is a schematic block diagram of the mode switching mechanism of
the combination camera head. The switching mode mechanism of the
light source is shown in FIG. 2. The preferred embodiment of the
mechanism requires the endoscope to be attached to the combination
light source 36 and the combination camera head 42 by means of the
endoscope connector 180. The combination light source 36 is capable
of providing white light (reflectance) illumination and blue light
(fluorescence excitation) illumination. The combination camera head
42 is capable of transducing three channel RGB reflectance images
and two channel fluorescence images.
Because the light source 36 and camera head 42 are physically
separate, the mode switching mechanism is composed of two parts.
The two parts of the mechanism are linked through control signals
via the imaging system control center 20 and the light source
system controller 90. Since the metal halide lamp 80 in the
combination light source 36 is capable of providing both the white
and blue light, a light source part of the mode switch consists of
the filter driver 94 and the white light an blue light filters 82.
The filter driver 94 responds to instructions from the light source
system controller 90 and positions the appropriate filter in the
light path between the lamp and the endoscope illumination guide.
The status of the filter driver 94 is also monitored by the light
source system controller 90, which then communicates with the
control center 20 via the interface to the status and control lines
102.
A second part of the mode switching mechanism is located in the
combination camera head 42. This part of the mode switching
mechanism 67 utilizes a movable light path directing mechanism such
as a mirror 186. When in the imaging system is in fluorescence
imaging mode, the mirror is moved out of the light path between the
endoscope eyepiece and the fluorescence camera head 44. In this way
the fluorescence light reaches the dichroic mirror 182 that
separates spectrally .DELTA..lambda..sub.1 and
.DELTA..lambda..sub.2 into their respective optical paths. When the
imaging system is in the white light imaging mode, the mirror 186
is moved into the light path. In this position, light from the
endoscope is directed to a second, fixed mirror 190, where the
light path is folded to form a periscope that redirects the light
from the endoscope eyepiece to the RGB video camera head 46.
The operation of both parts of the mode switching mechanism is
controlled by an operator input on the combination camera head 42.
The operator initiates a switch 65 to change the operation of the
imaging system. This results in a signal being sent to the control
center indicating that a switch of imaging modes has been
initiated. A signal is generated by a pair of electrical or optical
proximity switches 192, 194 in the combination camera head 42 that
sense the position of the movable mirror 186. A second signal is
generated by switches 192, 194 and sent to the control center 20
when the movable mirror 186 has reached its new position.
The switches 192, 194 function as a safety mechanism for the ICCDs
in the fluorescence camera head. When energized, the ICCDs are
susceptible to damage from bright light (e.g. white light
reflectance images from the endoscope eyepiece). If the movable
mirror 186 is not completely in the fluorescence mode imaging
position, the control center 20 reacts by immediately shutting off
the power to the ICCDs, thereby protecting them from exposure to
possibly damaging illumination.
The control center 20 reacts differently to the switch signals
depending on whether the operator is switching from fluorescence
imaging mode into the white light imaging mode or from white light
imaging mode into the fluorescence imaging mode. In the former
case, the control center 20 reacts to the first switch signal by
immediately shutting off the power to the ICCDs and stopping the
display of all images. When the control center 20 receives the
second switch signal, indicating that the movable mirror 186 in the
camera head 42 has reached the white light imaging mode position,
the control center sends a signal to the light source system
controller 90 instructing it to move the white light filter into
the light path. When the light source mode switch has completed the
filter change, the light source system controller 90 generates a
light source status signal, which is transmitted to the control
center 20. Upon receipt of the light source status signal, the
control signal routes the video signal from the RGB video camera
control unit 48 to the RGB video monitor 54 and the resulting white
light image is displayed.
In the case of switching from white light imaging mode into the
fluorescence imaging mode, the control center 20 reacts to the
first switch signal from the combination camera head 42 by sending
a signal to the light source system controller 90 instructing it to
move the blue light filter into the light path. A light source
status signal is generated and sent the control center 20 when the
light source mode switch has completed the filter change. When the
control center also receives the second switch signal from the
combination camera head 42, indicating that the movable mirror 186
has reached the fluorescence imaging mode position, the control
center energizes the ICCDs in the fluorescence camera head 44 and
routes the video signals from the fluorescence camera control units
to the RGB video monitor 54. The resulting fluorescence image is
displayed on the RGB video monitor 54. If the incorrect light
source status signal is received by the control center 20, the
ICCDs in the fluorescence camera head will not be energized, even
if the second switch signal has been received from the combination
camera head 42.
In accordance with another aspect of the present invention, the
imaging system of the present invention quantifies the relative
brightness of the autofluorescence light produced by the tissue in
each of the spectral bands .DELTA..lambda..sub.1 and
.DELTA..lambda..sub.2 in an objective manner. FIG. 7, shows a
monitor display 200 with an image 202 of the tissue under
examination. Differences in the autofluorescence spectrum produced
by normal and abnormal tissue are shown as areas of different color
in the image. For example, abnormal tissue 204 produces
proportionally less autofluorescence light in the green portion of
the spectrum than normal tissue and is shown as a reddish area in
the displayed image.
The relative brightness of the autofluorescence light in the green
and red wavebands imaged by the system, .DELTA..lambda..sub.1 and
.DELTA..lambda..sub.2, can be used as a measure of the difference
in the actual fluorescence emission spectra of normal and abnormal
tissue. A ratio (or other function relating the
.DELTA..lambda..sub.1 to the .DELTA..lambda..sub.2 waveband) of the
brightness of the tissue autofluorescence in the green and red
spectral bands is calculated and displayed to the physician. The
ratio is calculated for a small area such as a region 206 defined
in the center of the field of view. Since the color ratio can be
recalculated on a frame by frame basis in real time, the color
ratio displayed represents the average color ratio of the tissue
imaged within the bounds of area 206. Although the area 206 is
shown as a particular area located in the center of the field of
view, other locations within the field of view and larger or
smaller areas could be used.
The ratio calculation is implemented as follows: As described
above, the video signals from the fluorescence camera control units
are routed to the imaging board 28. The imaging board 28 digitizes
the video signals such that the video signal amplitudes correspond
proportionally to digital grey level values. The central processing
unit 22 within the control center 20 reads the data digitized by
the imaging board 28 and sums the grey level values of all the red
channel digital data within area 206 and divides that sum by the
sum of all the green channel data within area 206. The quotient of
these two sums is shown as a dimensionless number 208 on the
monitor.
As an alternative to displaying a dimensionless number, other
non-visual cues could be used to quantify the relative brightness
of the tissue autofluorescence in spectral wavebands
.DELTA..lambda..sub.1 and .DELTA..lambda..sub.2. For example, a
tone having a frequency that is dependent upon the ratio of the
brightness of the autofluorescence in each spectral band could be
produced. Similarly, the frequency of a blinking light could be
made to change in proportion to the changing ratio.
While the preferred embodiment of the invention has been
illustrated and described in the preceding description, it will be
appreciated that various changes can be made therein without
departing from the spirit and scope of the invention. The scope of
the invention is therefore to be determined from the following
claims and equivalents thereto.
APPENDIX A REM BASE ADDRESS OF BOARD HARDWIRED TO D0000 DEF SEG =
53248 REM READ OUT "AGC" LOGO GOSUB READLOGO REM INITIALIZE DAC'S
TO ZERO, SET-UP GAIN AND RANGE GOSUB CLEARDAC REM MAKESURE ICCD
POWER IS OFF GOSUB HVPSOFF REM STICK IN SOME STARTING VALUES FOR
THE GAIN CONTROL k0! = .72134/3: REM PORTION OF GAIN FACTOR OF
[-?.about.?] {0.5 V/ln(2)} skew! = 1: REM WEIGHTING SHIFT IF deln's
ON OPPOSITIE SIDES OF `1` REM skew <1 SHIFTS EMPHASIS TO LARGER
ERROR TERM tlo! = 60: REM LOW THRESHOLD IN PERCENTAGE OF FULLSCALE
thi! = 80: REM HIGH THRESHOLD IN PERCENTAGE OF FULLSCALE flo! = 50:
REM NOMINAL PERCENTAGE OF IMAGE ABOVE THRESHOLD ON CHANNEL 5 fhi! =
50: REM NOMINAL PERCENTAGE OF IMAGE ABOVE THRESHOLD ON CHANNEL 6
wlo! = 1!: REM FULL AUTO GAIN WEIGHTING FOR CHANNELS (2 & 5)
whi! = 1!: REM FULL AUTO GAIN WEIGHTING FOR CHANNELS (3 & 6)
dband! = .02: REM GAIN DEADBAND IN VOLTS rg0! = .014348: rg1! =
1.0494: rg2! = -.00048863#: REM L2PP6 +10% NUMS steps = 0: REM RED
INCREMENTS AROUND NOMINAL REM CHECK TO SEE IF A PREVIOUS
CALIBRATION FILE IS DESIRED 300 PRINT "USE PREVIOUS CALIBRATION
FILE (`df for default)?*y/n/q)" INPUT bob$: IF (bob$ = "q") THEN
10000 IF (bob$ = "n") THEN 680 IF (bob$ = "df") THEN name$ =
"default.age" GOTO 500 END IF IF (bob$ <> "y") THAN 300 PRINT
"ENTER THE FILENAME TO READ THE DATA FROM" INPUT name$ 500 OPEN
name$ FOR INPUT AS #1 INPUT #1, npcn2max!, npcn2min!, blklvl2%,
whtlvl2%, size2! INPUT #1, npcn3max!, npcn3min!, blklvl3%,
whtlvl3%, size3! INPUT #1, npcn5max!, npcn5min!, blklvl5%,
whtlvl5%, size5! IF (npcn3! > npcn3max!) THEN npcn3max! = npcn3!
IF (npcn5! > npcn5max!) THEN npcn5max! = npcn5! IF (npcn6! >
npcn6max!) THEN npcn6max! = npcn6! IF (npcn2! > npcn2min!) THEN
npcn2min! = npcn2! IF (npcn3! > npcn3min!) THEN npcn3min! =
npcn3! IF (npcn5! > npcn5min!) THEN npcn5min! = npcn5! IF
(npcn6! > npcn6min!) THEN npcn6min! = npcn6! REM GO AROUND AGAIN
1400 NEXT i 1450 NEXT j REM DETERMINE BLACK LEVEL REFERENCE VALUES
BY SLOWLY INCREASING REM REFERENCES UNTIL COUNTS IN EACH CHANNEL
FOR DARK IMAGE ARE REM ONE HALF OF FULL COUNTS POSSIBLE ON CHANNEL
REM SET UP FLAGS TO TRIGGER BLACK LEVEL REF VALUE SAVE 1600 flag2 =
0: flag3 = 0: flag5 = 0: flag6 = 0 REM SELECT NEW REFERENCE VOLTAGE
2110 lim% = 260 2120 FOR k% [-?=?] 130 TO lim% REM SKIP AHEAD IF
ALL THE BLACK LEVELS HAVE BEEN DETERMINED 2130 fsum = flag2 + flag3
+ flag5 + flag6 2140 IF (fsum > 3) THEN k% = lim% 2150 MSB% =
k%.backslash.16: REM DETERMINE HIGH BYTE lsb% = (k% - (MSB% * 16))
* 16: REM DETERMINE HIGH NIBBLE OF LOW BYTE REM NOW START
INCREASING REFERENCE LEVELS ON EACH COUNTER REM UNTIL COUNTS START
TO FALL OFF SIGNIFICANTLY 2230 POKE &H31, MSB%: POKE &H30,
lsb%: REM REF4 ==> CH6 POKE &H33, MSB%: POKE &H32, lsb%:
REM REF3 ==> CH5 POKE &H35, MSB%: POKE &H34, lsb%: REM
REF2 ==> CH3 POKE &H37, MSB%: POKE &H36, lsb%: REM REF1
==> CH2 POKE &H38, 0: REM UPDATE DAC'S 2400 GOSUB CLEARCNT
2420 fields1! PEEK(&H0): REM WAIT FOR REQUIRED # OF FIELDS IF
(fields1! <= 3) THEN 2420 2480 GOSUB READCNTS fields2! =
PEEK(&H0) REM CORRECT FIELDS TO AVERAGE IF IT INCREMENTED
DURING CHANNEL READS INPUT #1, npcn6max!, npcn6min!, blklvl6%,
whtlvl6%, size6! CLOSE #1: GOTO 7500: REM CLOSE INPUT AND SKIP OVER
CAL FUNCTIONS REM INITIALIZE PIXEL COUNTER MAX/MIN'S 680 npcn2max!
= 0: npcn3max! = 0: npcn5max! = 0: npcn6max! = 0: z! = 200000:
npcn2min! = z!: npcn3min! = z!: npcn5min! = z! npcn6min! = z! REM
LOOP THROUGH COUNTER READ CYCLES AND PICK OUT MAXIMUM REM AND
MINIMUM COUNTER VALUES . . . SHOULD CONTAIN MAXIMUM COUNTS REM IF
REFERENCE THRESHOLDS ARE SET BELOW BLACK LEVELS 710 FOR j = 0 TO 3:
REM GO THROUGH COUNTER SCANNING A FEW TIMES 720 FOR i = 0 TO 15:
REM VARY # OF FIELDS TO AVOID LATENCY INDUCED ALIASING 730 GOSUM
CLEARCNT REM LET COUNTERS FREE RUN FOR (93 - i) FIELDS 740 fields1!
= PEEK(&H0) IF (fields1! <= (92 - i)) THEN 740 REM READ OUT
ALL COUNTERS 810 GOSUB READCNTS fields2! = PEEK(&H0) REM
CORRECT FIELDS TO AVERAGE IF FIELDS INCREMENTED DURING READS
fields! = (fields1! + fields2!)/2 REM CALCULATE TOTAL COUNTS IN
EACH CHANNEL GOSUB MAKECNTS REM NORMALIZE COUNTER CONTENTS TO
NUMBER OF FIELDS TO REM DETERMINE FULL IMAGE COUNT VALUES 1000
npcn2! = ch2!/fields!: npcn3! = ch3!/fields! npcn5! = ch5!/fields!:
npcn6! = ch6!/fields! REM CHECK FOR UNREALISTIC FULL FILL IMAGE
COUNT VALUES 1100 flag% = 0: npcn! = 173000: REM npcn! SHOULD BY
NOMINAL COUNT VALUE 1120 IF (ABS(1 - (npcn2!/npcn!)) .05) THEN
flag% = 1 1130 IF (ABS(1 - (npcn3!/npcn!)) .05) THEN flag% = 1 1150
IF (ABS(1 - (npcn5!/npcn!)) .05) THEN flag% = 1 1160 IF (ABS(1 -
(npcn6!/npcn!)) .05) THEN flag% = 1 1170 IF (flag% > 0) THEN
730: REM GO BACK AND START OVER REM CHECK FOR HIGHER THAN OR LOWER
THAN PREVIOUS EXTREMES 1210 IF (npcn2!>npcn2max!) THEN npcn2max!
= npcn2! fields! (fields1! + fields2!)/2 GOSUB MAKECNTS REM
NORMALIZE COUNTER CONTENTS TO NUMBER OF FIELDS 2900 npcn2! =
ch2!/fields!: npcn3! = ch3!/fields! npcn5! = ch5!/fields!: npcn6! =
ch6!/fields! REM CHECK TO SEE IF NEW REFERENCE THRESHOLDS HAVE
ELIMINATED REM 50% OF POSSIBLE COUNTS ON EACH CHANNEL. IF YES, SET
FLAG REM AND ASSIGN CURRENT SETTING AS THIS CHANNELS BLACK LEVEL
3030 IF ((flag2 = 0) AND (npcn2! < (.5* npcn2max!)) THEN flag2 =
1 blklvl2% = k% END IF 3060 IF ((flag3 = 0) AND (npcn3! < (.5*
npcn3max!)) THEN flag3 = 1 blklvl3% = k% END IF 4020 IF ((flag5 =
0) AND (npcn5! < (.5* npcn5max!)) THEN flag5 = 1 blklvl5% = k%
END IF 4050 IF ((flag6 = 0) AND (npcn6! < (.5* npcn6max!)) THEN
flag6 = 1 blklvl5% = k% END IF 4080 NEXT k% REM DETERMINE FULLSCALE
(WHITE) REFERENCE LEVEL BY RAISING GAINS REM UNDER USER CONTROL
UNTIL SATURATION APPEARS IN EACH COLOR IN REM THE IMAGE THEN LOCK
INTENSIFIER GAINS AND RAISE CHANNEL REM REFERENCE VOLTAGES UNTIL
MAJORITY OF COURTS HAVE BEEN ELIMINATED. REM CORRESPONDING
REFERENCE VOLTAGE IS THEN DEFINED AS "FULL SCALE". 4500 GOSUB
HVPSON PRINT "PREPARING TO INCREASE INTENSIFIER GAINS" PRINT
"PLEASE ESTABLISH THE DESIRED ILLUMINATION" PRINT
"++++++++++++++++++++WARNING++++++++++++++++++" PRINT "+DO NOT
ADJUST THE ILLUMINATION DURING WHITE LEVEL SCANNING+" PRINT
"+++++++++++++++++++++++++++++++++++++++++++++" 4520 PRINT "TYPE
`r` WHEN READY, OR `q` TO QUIT" INPUT com$: IF (com$ = "q") THEN
1000: IF (com$ <> "r") THEN 4520 REM DETERMINE THE REQUIRED
INTENSIFIER SETTING TO REM PROVIDE SOME SATURATION FOR EACH COLOR
CHANNEL 4600 PRINT "TYPE `u` TO RAISE OR `d` TO DECREASE THE RED
GAIN" PRINT "TYPE ANY OTHER KEY TO GO ON TO GREEN CHANNEL" 4620
msb1% = 100: REM STARTING RED VALUE 4630 INPUT dir$ 4640 IF ((dir$
<> "u") AND (dir$ <> "d")) THEN sat1% = msb1%: REM SAVE
CURRENT RED GAIN AS SATURATION GAIN POKE&[H53?], 0:
POKE&H58, 0: REM RESET RED GAIN TO ZERO GOTO 4800: REM JUMP TO
GREEN CHANNEL GAIN SET UP END IF 4650 IF ((dir$ = "u") AND (msb1%
<200)) THENmsb1% = msb1% + 4 IF ((dir$ = "d") AND (msb1% >0))
THENmsb1% = msb1% - 4 POKE&H53, msb1%: POKE&H58, 0: GOTO
4630 4800 PRINT "TYPE `u` TO RAISE OR `d` TO DECREASE THE GREEN
GAIN" PRINT "TYPE ANY OTHER KEY TO GO ON" 4820 msb2% = 100: REM
STARTING RED VALUE 4830 INPUT dir$ 4840 IF ((dir$ <> "u") AND
(dir$ <> "d")) THEN sat2% = msb2%: REM SAVE CURRENT RED GAIN
AS SATURATION GAIN POKE&H51, 0: POKE&H58, 0: REM RESET RED
GAIN TO ZERO GOTO 5000 END IF 4650 IF ((dir$ = "u") AND (msb2%
<200)) THEN msb2% = msb2% + 4 IF ((dir$ = "d") AND (msb2%
>0)) THEN msb2% = msb2% 4 POKE&H51, msb2%: POKE&H58, 0:
GOTO 4830 5000 PRINT "WERE BOTH GAINS SET PROPERLY? (y/n/q)" INPUT
bob$: IF (bob$ = "q") THEN 10000 IF (bob$ = "n") THEN 4500 IF (bob$
<> "y") THEN 5000 REM IF ALL WAS WELL, RESET SATURATION GAIN
VOLTAGES REM ON RED AND GREEN AND CONTINUE 5060 POKE &H53,
sat1%: POKE &H51, sat2%: POKE &H58, 0 REM PAUSE TO LET ICCD
[IIVPS? HVPS?] SETTLE 5070 FOR i = 1 TO 20000: NEXT i REM DETERMINE
WHITE LEVEL BY INCREASING THRESHOLDS REM UNTIL ALMOST ALL COUNTS
ARE ELIMINATED REM SET UP FLAGS TO TRIGGER WHITE LEVEL REF VALUE
SAVE 5090 flag2 = 0: flag3 = 0: flag5 = 0: flag6 = 0 max% = 2000
REM SELECT NEW REFERENCE VOLTAGE 5110 FOR k% = 1500 TO max% REM
SKIP AHEAD IF ALL THE WHITE LEVELS HAVE BEEN DETERMINED 5120 fsum =
flag2 + flag3 + flag5 + flag6 5130 IF (fsum > 5) THEN k% = max%
MSB% = k%.backslash.16: REM HIGH BYTE lsb% = (k% - (MSB% * 16)) *
16: REM LOW BYTE POKE &H31, MSB%: POKE &H30, lsb%: REM REF4
==> CH6 POKE &H33, MSB%: POKE &H32, lsb%: REM REF3
==> CH5 POKE &H35, MSB%: POKE &H34, lsb%: REM REF2
==> CH3 POKE &H37, MSB%: POKE &H36, lsb%: REM REF1
==> CH2 POKE &H38, 0: REM UPDATE DAC'S 5400 GOSUB CLEARCNT
5420 fields1! = PEEK(&H0): REM WAIT FOR REQUIRED # OF FIELDS IF
(fields1! <= 9) THEN 5420 5480 GOSUB READCNTS fields2! =
PEEK(&H0) REM CORRECT FIELDS TO AVERAGE IF IT INCREMENTED
DURING CHANNEL READS fields! = (fields1! + fields2!)/2 GOSUB
MAKECNTS REM NORMALIZE COUNTER CONTENTS TO NUMBER OF FIELDS pcn2! =
ch2!/fields!: pcn3! = ch3!/fields! pcn5! = ch5!/fields!: pcn6! =
ch6!/fields! REM CHECK TO SEE IF NEW REFERENCE THRESHOLDS HAVE
ELIMINATED REM 99% OF POSSIBLE COUNTS ON EACH CHANNEL. IF YES, SET
FLAG REM AND ASSIGN CURRENT SETTING AS THIS CHANNELS BLACK LEVEL
6020 IF ((flag2 = 0) AND (pcn2! < (.015 * npcn2max!))) THEN
flag2 = 1 whtlvl2% = k% END IF 6040 IF ((flag3 = 0) AND (pcn3! <
(.015 * npcn3max!))) THEN flag3 = 1 whtlvl3% = k% END IF 6080 IF
((flag5 = 0) AND (pcn5! < (.015 * npcn5max!))) THEN flag5 = 1
whtlvl5% = k% END IF 6100 IF ((flag6 = 0) AND (pcn6! < (.015 *
npcn6max!))) THEN flag6 = 1 whtlvl6% = k% END IF 6130 NEXT k% REM
DETERMINE THE IMAGE SIZE AS A FRACTION OF THE AVAILABLE IMAGE REM
AREA BY ADJUSTING THE REFERENCE VOLTAGES TO "JUST" ABOVE BLACK
REM AND COUNTING ALL THE PIXELS THAT EXCEED THIS THRESHOLD REM
`up!` IS THE FRACTIONAL INCREASE (IN TERMS OF THE SIGNAL REM INPUT
RANGE) IN THE THRESHOLD ABOVE THE PREVIOUSLY REM DETERMINED BLACK
LEVEL (IN MSB) 6200 up! = .05: REM CALCULATE THRESHOLDS
CORRESPONDING TO 5% FULLSCALE lvl2% = blklvl2% + ((whtlvl2% -
blklvl2%) * up!) lvl3% = blklvl3% + ((whtlvl3% - blklvl3%) * up!)
lvl5% = blklvl5% + ((whtlvl5% - blklvl5%) * up!) lvl6% = blklvl6% +
((whtlvl6% - blklvl6%) * up!) REM LOAD THRESHOLDS POKE &H37,
(lvl2%.backslash.16): REM CH2 MSB POKE &H36, (lvl2% -
((lvl2%.backslash.16) * 16)) * 16): REM CH2 LSB POKE &H35,
(lvl3%.backslash.16): REM CH3 MSB POKE &H34, (lvl3% -
((lvl2%.backslash.16) * 16)) * 16): REM CH3 LSB POKE &H33,
(lvl5%.backslash.16): REM CH5 MSB POKE &H32, (lvl5% -
((lvl2%.backslash.16) * 16)) * 16): REM CH5 LSB POKE &H31,
(lvl6%.backslash.16): REM CH6 MSB POKE &H30, (lvl6% -
((lvl2%.backslash.16) * 16)) * 16): REM CH6 LSB POKE &H38, 0:
REM UPDATE DAC'S 6700 oops% = 0: num% = 4 6710 FOR j% = 0 TO num%
6730 GOSUB CLEARCNT 6740 fields1! = PEEK(&H0): REM WAIT FOR
REQUIRED # OF FIELDS IF (fields1! <= 91) THEN 6740 6780
GOSUBREADCNTS fields2! = PEEK*&H0) REM CORRECT FIELDS TO
AVERAGE IF IT INCREMENTED DURING CHANNEL READS fields! = (fields1!
+ fields2!)/2 GOSUB MAKECNTS REM NORMALIZE COUNTER CONTENTS TO
NUMBER OF FIELDS pcnsize2! = ch2!/fields!:pcnsize3! = ch3!/fields!
pcnsize5! = ch5!/fields!:pcnsize6! = ch6!/fields! REM CALCULATE AND
CHECK FRACTIONAL SIZE OF IMAGE ON EACH CHANNEL 7270 size2! =
pcnsize2!/npcn2max! IF (size2! > 1.1 OR size2! < .2) THEN
oops% = 1 7290 size3! = pcnsize3!/npcn3max! IF (size3! > 1.1 OR
size3! < .2) THEN oops% = 1 7330 size5! = pcnsize5!/npcn5max! IF
(size5! > 1.1 OR size5! < .2) THEN oops% = 1 7350 size6! =
pcnsize6!/npcn6max! IF (size6! > 1.1 OR size6! < .2) THEN
oops% = 1 7370 IF (oops% = 0) THEN j% = num% 7380 NEXT j% 7400 IF
(oops% <> 0) THEN PRINT "INVALID IMAGE SIZES FOUND" GOTO
10000 END IF REM SHUT DOWN INTENSIFIER GAIN AND POWER 7430 GOSUB
GAINZERO GOSUB HVPSOFF REM PRINT OUT RESULTS 7500 PRINT "CHANNEL
MAXCNT MINCNT BLKLVL WHTLVL SIZE%" PRINT "2 "; npcn2max!;" ";
npcn2min!;" "; blklvl2%;" "; whtlvl2%;" "; size2! PRINT "3 ";
npcn3max!;" "; npcn3min!;" "; blklvl3%;" "; whtlvl3%;" "; size3!
PRINT "5 "; npcn5max!;" "; npcn5min!;" "; blklvl5%;" "; whtlvl5%;"
"; size5! PRINT "6 "; npcn6max!;" "; npcn6min!;" "; blklvl6%;" ";
whtlvl6%;" "; size6! REM WRITE CURRENT SETTINGS TO FILE 7570 PRINT
"DO YOU WANT TO SAVE THESE TO A FILE? (y/n/q)" 7580 INPUT bob$: IF
(bob$ = "q") THEN 10000 IF (bob$ = "n") THEN 7640 IF (bob$ <>
"y") THEN 7570 7610 PRINT "ENTER THE FILENAME TO SAVE THE DATA
UNDER" 7620 INPUT name$ 7630 OPEN name$ FOR OUTPUT AS #1 PRINT #1,
npcn2max!, npcn2min!, blklvl2%, whtlvl2%, size2! PRINT #1,
npcn3max!, npcn3min!, blklvl3%, whtlvl3%, size3! PRINT #1,
npcn5max!, npcn5min!, blklvl5%, whtlvl5%, size5! PRINT #1,
npcn6max!, npcn6min!, blklvl6%, whtlvl6%, size6! CLOSE #1 REM
REBUILD `pcnsize` VARIABLES 7640 pcnsize2! = size2! * npcn2max!:
pcnsize3! = size3! * npcn3max! pcnsize5! = size5! * npcn5max!:
pcnsize6! = size6! * npcn6max!
REM++++++++++++++++++++++++++++++++++++++++++++++ REM REM AGC
FEEDBACK DETERMINATION REM
REM++++++++++++++++++++++++++++++++++++++++++++++ 7680 PRINT "
PREPARING TO ENTER IMAGING MODE" PRINT " PLEASE ESTABLISH THE
DESIRED ILLUMINATION" PRINT "TYPE `r` WHEN READY, OR `q` TO QUIT"
INPUT com$: IF (com$ = "q") THEN 10000: IF (com$ <> "r") THEN
7680 7700 PRINT "SELECT GAIN CONTROL METHOD" PRINT "m -> MANUAL,
f -> full (MIXED PEAK/AVERAGE)" INPUT agcmode$ IF (agcmode$ =
"m") THEN PRINT "USE UP/DOWN ARROW KEYS TO CONTROL FINE GAIN" PRINT
"USE PGUP/PGDOWM[N/?] KEYS TO CONTROL COARSE GAIN" GOTO 7900 END IF
IF (agcmode$ = "f") THEN GOTO 7900 GOTO 7700 REM SET UP DEFAULT
THRESHOLDS 7900 temp% = CINT((whtlvl2% - blblvl2%)/16 * (tlo!/100))
POKE &H37, temp% REM SET REF3 AT ABOUT thi% FS IN MSB temp% =
CINT((whtlvl3% - blblvl3%)/16 * (tli!/100)) POKE &H35, temp%
REM SET REF5 AT ABOUT tlo% FS IN MSB temp% = CINT((whtlvl5% -
blblvl5%)/16 * (tlo!/100)) POKE &H33, temp% REM SET REF6 AT
ABOUT thi% FS IN MSB temp% = CINT((whtlvl6% - blblvl6%)/16 *
(thi!/100)) POKE &H31, temp% POKE &H38, 0: REM UPDATE DAC'S
GOSUB HVPSON PRINT "ENABLING ICCD HVPS" now = TIMER DO WHILE (now =
TIMER) LOOP REM START CHECKING COUNTERS delt0! = 1: delt1! = 1:
delt2! = 1 CLS REM SET UP FAULT VARIABLE warn% = 0: REM CHECKED FOR
>15 FAULTS OUT AND DISABLES ICCD'S 8000 DO WHILE (1 <> 0)
key$ = INKEY$ IF ((key$ = "q") or (key$ = "Q")) THEN 9200 IF ((key$
<> CHR$(0)) AND (agemode$ <> "m")) THEN GOSUB MODVALS:
REM TWEAK RUNNING PARAMETERS REM DELAY AND THEN READ REQUIRED
NUMBER OF FIELDS 8070 (fields1! = PEEK(&H0) IF (fields1! <=
3) THEN 8070 GOSUB CLEARCNT 8080 FIELDS1! = peek(&[H0?]) if
(fields1! <= 0) THEN 8080 8180 GOSUB READCNTS fields2! =
PEEK(&H0) REM CORRECT FIELDS TO AVERAGE IF IT INCREMENTED
DURING CHANNEL READS fields! = (fields1! + fields2!)/2 GOSUB
MAKECNTS REM NORMALIZE COUNTS TO NUMBER OF FIELDS AND FULL IMAGE
COUNTS REM I.E. `sx!` IS (AREA ABOVE THRESHOLD/MAXIMUM IMAGE SIZE)
s2! = ch2!/fields!/pcnsize2!: s3! = ch3!/fields!/pcnsize3! s5! =
ch5!/fields!/pcnsize5!: s6! = ch6!/fields!/pcnsize6!
REM+++++++++++SIMPLE PSEUDO-PROPORTIONAL AGC WITH
DEADBAND+++++++++++++++++++ REM+++ERROR TERM BASED UPON WEIGHTED
AVERAGE OF INDIVIDUAL ERRORS+++++ REM++++++++++++++++FOUR SAMPLE
LEAKY INTEGRAL ACTION+++++++++++++++++++++ REM CAN'T HAVE MORE THAN
ALL THE IMAGE 8700 IF (s2! > 1) THEN s2! = 1: IF (s3! > 1)
THEN s3! = 1 IF (s5! > 1) THEN s5! = 1: IF (s6! > 1) THEN s6!
= 1 REM RELATIVE AMOUNT OF IMAGE IN RELATION TO DESIRED LEVEL del2!
= (s2!/(flo!/100)) del3! = (s3!/(thi!/100)) del5! =
(s5!/(flo!/100)) del6! = (s6!/(thi!/100)) REM SKIP PAST AUTOMATIC
GAIN CHANGE DETERMINATION IF IN MANUAL MODE IF (agcmode$ = "m")
THEN GOSUB MANUALdg GOTO 8850 END IF REM CHECK FOR SEVERE
OVERSATURATION CONDITIONS IF ((del2! > 6) OR (del6! > 6))
THEN warn% = warn% - 1: REM CHARGE WARNING VALUE ELSE warn% = warn%
+ 1: REM DISCHARGE WARNING VALUE IF (warn% < 0) THEN warn% = 0
END IF REM IF SATURATED TO[TOO/?] MANY TIMES IN A ROW, CRASH AND
BURN IF (warn% > 25)THEN GOSUB HVPSOFF FOR i = 58 TO 74 STEP 4
SOUND (EXP(i/10)), 1 NEXT i PRINT "AGC UNABLE TO PREVENT SERIOUS
SATURATION" PRINT "PLEASE VERIFY SYSTEM SETTINGS AND CONFIGURATION"
GOTO 9200 END IF IF (warn% > 16) THEN SOUND 3600, 1 REM
ARBITRATE GAIN CONTROL INPUTS BASED UPON REM RELATIVE RED AND GREEN
IMAGE FILLS IF ((del5! >= del2!) AND (del6! >= del3!)) THEN
REM GREEN IMAGE CONTAINS HIGHEST RELATIVE IMAGE FILLS THEREFORE REM
GENERATE A WEIGHTED ERROR VALUE ONLY FROM GREEN VALUES IF (SGN(1 -
del5!) = SGN(1 - del6!)) THEN delt3! = ((wlo! * del5!) + (whi! *
del6!)) delt3! = delt3!/(wlo! + whi!) MODE$ = "5AND6" END IF IF
((del5! < 1) AND (del6! > 1)) THEN REM SLIGHTLY SHIFT
WEIGHTING TOWARDS CHANNEL 5 delt3! = ((skew! * wlo! * del5!) +
(whi!/skew! * dcl6!)) delt3! = delt3!/(skew! * wlo! + whi!/skew!)
MODE$ + "5OVER6" END IF IF ((del6! < 1) AND (del5! > 1)) THEN
REM SLIGHTLY SHIFT WEIGHTING TOWARDS CHANNEL 6 delt3! =
((wlo!/skew! * del5!) + (skew! * whi! * dcl[del?]6!)) delt3! =
delt3!/(wlo!/skew! + skew! * whi!) MODE$ + "6OVER5" END IF ELSEIF
((del2! >= del5!) AND (del3! >= del6!)) THEN REM RED IMAGE
CONTAINS HIGHEST RELATIVE IMAGE FILLS THEREFORE REM GENERATE A
WEIGHTED ERROR VALUE ONLY FROM RED VALUES IF (SGN(1 - del2!) =
SGN(1 - del3!)) THEN delt3! = ((wlo! * del2!) + (whi! * del3!))
delt3! = delt3!/(wlo! + whi!) MODE$ = "2AND3" END IF IF ((del2!
< 1) AND (del3! > 1)) THEN REM SLIGHTLY SHIFT WEIGHTING
TOWARDS CHANNEL 2 delt3! = ((skew! * wlo! * del2!) + (whi!/skew! *
del3!)) delt3! = delt3!/(skew! * wlo! + whi!/skew!) MODE$ =
"2OVER3" END IF IF ((del3! < 1) AND (del2! > 1)) THEN REM
SLIGHTLY SHIFT WEIGHTING TOWARDS CHANNEL 3 delt3! = ((wlo!/skew! *
del2!) + (skew! * whi! * del3!)) delt3! = delt3!/(wlo!/skew! +
skew! * whi!) MODE$ + "3OVER2" END IF REM IF NEITHER RED OR GREEN
IS CLEARLY DOMINANT, MIX RESULTS REM TO GENERAL AN ERROR TERM
ELSEIF ((del5! >= del2!) AND (del3! >= del6!)) THEN REM GREEN
MID AND RED PEAK IF (SGN(1 - del5!) = SGN(1 - del3!)) THEN delt3! =
((wlo! * del5!) + (whi! * del3!)) delt3! = delt3!/(wlo! + whi!)
MODE$ = "5AND3" END IF IF ((del5! < 1) AND (del3! > 1)) THEN
REM SLIGHTLY SHIFT WEIGHTING TOWARDS CHANNEL 5 delt3! = (skew! *
wlo! * del5!) + (whi!/skew! * del3!)) delt3! = delt3!/(skew! * wlo!
+ whi!/skew!) MODE$ = "5OVER3" END IF IF ((del3! <= 1) AND
(del5! > 1)) THEN REM SLIGHTLY SHIFT WEIGHTING TOWARDS CHANNEL 3
delt3! = ((wlo!/skew! * del5!) + (skew! * whi! * del3!)) delt3! =
delt3!/(wlo! /skew!+ skew! * whi!) MODE$ = "3OVER5" END IF ELSEIF
((del2! >= del5!) AND (del6! >= del3!)) THEN REM RED MID AND
GREEN PEAK IF (SGN(1 - del2!) = SGN(1 - del6!)) THEN
delt3! ((wlo! * del2!) + (whi! * del6!)) delt3! = delt3!/(wlo!
whi!) MODE$ = "2AND6" END IF IF ((del2! < 1) AND (del6! > 1))
THEN REM SLIGHTLY SHIFT WEIGHTING TOWARDS CHANNEL 2 delt3! =
((skew! * wlo! * del2!) + (whi!/skew! * del6!) delt3! =
delt3!/(skew! * wlo! + whi!/skew!) MODE$ = "2OVER6" END IF IF
((del6! < 1) AND (del2! > 1)) THEN REM SLIGHTLY SHIFT
WEIGHTING TOWARDS CHANNEL 6 delt3! = ((who!/skew! * del2!) + (skew!
* whi! * del6!)) delt3! = delt3!/(wlo!/skew! + skew! * whi!) MODE$
= "6OVER2" END IF ELSE REM IF SITUATION GETS TO HERE, MUST HAVE
MISSING TEST CASE REM RUN IN SMALL CIRCLES AND PANIC BEEP LOCATE
20, 18 PRINT "del2="; del2!, "del3="; del3!," del5="; del5!,
"del6="; del6! GOTO10000 END IF REM FOUR SAMPLE INTEGRATOR WITH
GEOMETRIC DECAY `1/{(t-t0) 2}`
REM+++++++++++++++++++++++++++++++++++++++++++++++++++++++++ REM
BUILD delt! FROM RECENT GAIN CHANGE HISTORY OF dcltn!'s 8720 delt!
= (delt3! + delt2!/3 + delt1!/9 + delt0!/27) delt! - delt!/(1 + 1/3
+ 1/9 + 1/27): REM PRESERVE SCALE REM SHIFT deltn!'s ONE PERIOD
OLDER delt0! = delt1!: delt1! = delt2!: delt2! = delt3! REM PROTECT
`LOG` FROM NEAR ZERO OR LARGE `delt!` VALUES IF (delt! <
.000001) THEN delt! = .000001: REM LIMITS MAXIMUM DOWN STEP IF
(delt! > 1000000) THEN delt! = 1000000: REM LIMITS MAXIMUM UP
STEP REM LOG RESPONSE TO COMPLEMENT (e V) BEHAVIOR[BEHAVIOR /?] REM
NOTE THAT LARGE delt! CAUSES NEGATIVE dg! dg! = -1 * LOG(delt!) *
k0! IF (dg! > 2) THEN dg! = 2: REM OVERRIDE MAXIMUM UP STEP REM
NOW APPLY GAIN CHANGE, DEADBAND AND FAILURE LIMITS 8800 IF
(ABS(dg!) <= dband!) THEN dg! = 0: REM APPLY DEADBAND REM APPLY
GAIN CHANGE REM --> ASSUMES RED AND GREEN HAVE SIMILAR d/dV
{Krel[?]} CHARACTERISTICS 8850 g! = g! + dg! IF (g! < .01) THEN
g! = .01: REM BOTTOM GAIN LIMIT IF (g! > 9.3) THEN g! = 9.3: REM
TOP GAIN LIMIT gain% = g! * 4096/10: REM GREEN GAIN SETTING IN
PARTS PER 4096 REM SEND OUT NEW INTENSIFIER GAIN REQUESTS 8900
grnmsb% = gain%.backslash.16 grnlsb% = (gain% - (grnmsb% * 16)) *
16 r! = rg0! + g! * rg1! + (g! 2) * rg2!: REM RED GAIN IN VOLTS
rgain% = CINT((r! * 4096)/10): REM RED GAIN SETTING IN PARTS PER
4096 redmsb% = rgain%.backslash.16 redlsb% = (rgain% - (redmsb% *
16)) * 16 REM SEND OUT NEW CONTROL VOLTAGES 9000 POKE &H53,
redmsb%: POKE &H52, redlsb% POKE &H51, grnmsb%: POKE
&H50, grnlsb% POKE &H58, 0 locate 16, 27 format3$ =
" #.## #.##&&" COLOR 14 PRINT USING format3$; "GRN ="; g!;
"RED =";r!;" ";MODE$ LOCATE 19, 20 COLOR 4 format4$ =
" #.## #.## #.## #.##" PRINT USING format4$; "del2="; del2!;
"del3="; del3!; "del5="; del5!; "del6=": del6! 9100 LOOP
* * * * *